When do you need to use a regenerative resistor in Delta's servo drive?
When do you need to use a regenerative resistor in Delta's servo drive?

When a fault, ALE05 (Regeneration Error) is detected in the servo unit, it indicates that the regenerative energy has returned from the load to the servo drive and exceeds the processing capacity. This energy will be transmitted to the DC bus capacitance and will result in the voltage increase. When the voltage rises too high, the servo system needs to dissipate the extra energy using a regenerative resistor. The ASDA-A2 series servo drive provides a built-in regenerative resistor as standard factory. Users can also connect an external regenerative resistor if more regenerative capacity is needed. The following table shows the servo drive's built-in regenerative resistor specifications and the amount of regenerative power (average value) it can process.

ASDA-A2 220V series

ASDA-A2 400V Series

Please pay close attention to the following notes when using a regenerative resistor.

  1. Make sure the resistance (P1-52) and power (P1-53) values are correctly set.
  2. When installing an external regenerative resistor, make sure its resistance value is the same as the resistance of the built-in regenerative resistor. If combining several small capacity regenerative resistors in parallel to increase the capacity of the regenerative resistor, make sure the regenerative resistor resistance value complies with the specifications listed in the table above.
  • In general, when the amount of regenerative energy (average value) that can be processed is below the rated load ratio, the resistance temperature will increase to 120°C or more (when regeneration takes place continuously). For safety reasons, forced ventilation is a good way to reduce the temperature of regenerative resistors. We also recommend using regenerative resistors with thermal switches. For the load characteristics of regenerative resistors, consult the manufacturer.
  1. When using an external regenerative resistor, connect it to P and C and make sure the circuit between P and D is open. We recommend using external regenerative resistors with resistance values that follow the table above (Built-in Regenerative Resistor Specifications).


Reference: User Manual – ASDA-A2, page 50 (2.8 Selection of Regenerative Resistor).